1. Field of the Invention
The present invention relates to a fabrication method, particularly to a method for fabricating a nanoscale thermoelectric device.
2. Description of the Related Art
Few years ago, Intel Company announced that the dual-core microprocessor would replace the single-core microprocessor because the development of the existing single-core microprocessor had reached its ultimate. Under the current packaging design, increasing the working clock of the single-core microprocessor will generate much more heat and obviously increase the heat-dissipation cost without increasing the performance equally. Therefore, a 65-nm dual-core process is a necessary approach to promote the performance of microprocessors. However, the miniaturized, high-speed, and high performance chips bear the problem of heat dissipation. If the problem of heat dissipation cannot be resolved, many key elements in the fields of communication, optoelectronics, power, aerospace and biomedicine will be influenced. From the above discussion, it can be seen that heat management plays a very important role in the advanced chips.
Important heat-dissipation materials include: heat pipes, thermal interface materials and thermoelectric materials. Refer to FIG. 1. A thermoelectric element may include two different materials (such as a P-type semiconductor 10 and an N-type semiconductor 12) and a load 14, which form a loop. When there is a temperature difference between the ends of the P-type semiconductor 10 and the N-type semiconductor 12, a current will appear in the loop. In other words, the thermoelectric element can directly convert heat into electricity. A Taiwan patent of Publication No. I280649 uses thermoelectric semiconductor blocks to build a thermoelectric element. However, the thermoelectric element has a poor thermoelectric conversion efficiency because it has larger dimensions. A Taiwan patent of Publication No. I266401 uses a single type of material to build a thermoelectric element. However, the thermoelectric element also has a poor thermoelectric conversion efficiency because it only uses a single type of element. A Taiwan patent of Publication No. I262221 uses a hydraulic method to fabricate nanoscale wires and uses an aluminum baseplate as the substrate of the template of the nanoscale wires. The prior art is not suitable to fabricate nanoscale wires having a melting point close to or higher than the melting point of aluminum. In a technical literature, by J. R. Lim, J. F. Whitacre, J. P. Fleurial, C. K. Huang, M. A. Ryan, N. V. Myung, Adv. Mater. 2005, 17, 1488, an electrodeposition method is used to deposit a Bi2Te3 (N-type) nanoscale wire and a BiSbTe (P-type) nanoscale wire on a template, and then a photolithographic technology and photomasks are used to fabricate an element. The prior art is usually adopted. However, the equipment is expensive, and the fabrication process is complicated, and the environmental control is rigid. Therefore, the prior art is not suitable for mass production. The electrodeposition method itself is a simple process. However, electrodeposition is apt to have impurities and is hard to control alloy composition, particularly the composition of a more than ternary alloy.
Accordingly, the present invention proposes a method for fabricating a nanoscale thermoelectric device to overcome the abovementioned problems, whereby a thermoelectric element having P-type and N-type nanoscale wires can be fabricated, and whereby the alloy compositions of the nanoscale wires can be precisely controlled.